This invention relates to a pressure relief device for a pressure vessel and more particularly to such a pressure relief device having a large flow capacity when actuated.
Heretofore, such as illustrated in U.S. Pat. No. 4,388,940 dated June 21, 1983, pressure relief devices having a relatively large discharge opening and flow capacity have been utilized in pressure vessels. However, pressure relief devices that are utilized with fixed pressure vessels normally do not have tight space restrictions and a discharge opening for such a fixed pressure vessel can be of practically any desired size or diameter. Thus, such pressure relief devices for fixed pressure vessels do not normally have to be designed specifically for fitting within a restricted space while having a sufficient flow area for the large discharge opening required for the discharge of lading upon the reaching of a predetermined high fluid pressure within the pressure vessel.
Further, a relatively large diameter actuating spring for seating the valve closure is normally utilized and if the spring extends upwardly into the discharge opening the flow area for the discharge opening is restricted by the spring. In such pressure relief devices for fixed pressure vessels, a relatively large mounting area compared to the flow area has been provided. For example, in the pressure relief device shown in U.S. Pat. No. 4,388,940 the diameter of the spring which extends into the discharge opening or flow area and forms the mounting area is around one-third the diameter of the entire discharge opening and thus occupies a large central mounting area within the discharge opening.
Additionally, in the event it has been necessary heretofore to replace the resilient or elastomeric sealing element for the closure member, it has normally required removal of the valve from the pressure vessel or disassembly of the valve. Thus, replacement of a sealing element has been time-consuming and expensive.